26 University of California Publicatiotis ill Zoologij [Vol. 16 



The posterolateral flagellimi {post. lat. ft.) arises from the blepharo- 

 plast, passes posteriorly in the cytoplasm {intracijt. post. lat. fl.) close 

 to and parallel with the axostyle on its ventral side to about the level 

 of the middle of the nucleus, then diverges about 15°-25° from the 

 axostyle along the outer margin of the triangular halo (tri. halo) to 

 emerge from the cytoplasm as a free flagellum {post. lat. ft.) at a 

 little more than midway between the points of emergence of the 

 antero-lateral and the posterior flagella. The lower end of the intra- 

 cytoplasmie part of the flagellum is often somewhat thickened and 

 there is sometimes a small basal granule at the point of emergence not 

 found in 6. rmtris. 



The posterior flagellum {post, ft.) springs from the posterior 

 granule {po.st. has. gr.) on the tip of the axostyle which represents 

 its intracytoplasmic part fused with that of its mate. 



The free ventral flagellum has no prolonged intracytoplasmic part 

 and cannot be traced to the blepharoplast. It emerges from a vaguely 

 and somewhat diffusely stained axostyle, and usually extends pos- 

 teriorly, but has great freedom of action and may extend anteriorly. 

 The two ventral flagella often act in unison and often lie parallel to 

 one another or to the postero-lateral flagella. 



The flagella are long, about 1.5 the length of the body, and are 

 subequal in length. They serve not only for locomotion but also to 

 keep the surounding medium in motion when the parasite is fixed upon 

 the epithelial cells of its host by the ventral sucker-like eytostome. 



The axostyle {ax.) is a single organ (splitting into two in the pro- 

 phase of mitosis, as in fig. 1). axially located, and extending along 

 the ventral surface from near the center of the eytostome to the pos- 

 terior tip where it ends in a chromatic basal granule. It is somewhat 

 denser than the surrounding cytoplasm, somewhat chromatic but less 

 so than other parts of the neuromotor apparatus. It is homogeneous 

 throughout and clearly delimited from the adjacent cytoplasm. It 

 represents the intracytoplasmic part of the two posterior flagella (.see 

 Kofoid and Swezy, 1915a, b). 



It bears on each corner of its anterior end the deeply stained 

 ellipsoidal blepharoplast {I. bleph.) imbedded in its substance and 

 directly connected with the nucleus and centrosome and karyosome 

 by the rhizoplast. It also gives rise directly to the antero-lateral and 

 po.stero-lateral flagella, and, by waj' of the axostyle, to the posterior 



